There's a big difference between "no drop off fee" and the base rate being identical for OW versus RT rentals.

The only rentals in recent years where I have seen a "drop off fee" was on rentals within the same metro area (i.e. rent at KDAL, return at KDFW or Local Edition branch in same market).

True one-way rentals (and I do lots of these) don't have a drop off fee but usually have a MUCH higher base rate than RTs being returned to same location.

There are, of course, oddball exceptions where OWs are a lot cheaper than RTs. These instances are rare but when Hertz needs to move cars around they happen. There are some reliably good deals on OW rentals FROM Arizona or Florida in late spring, for example.